The present invention relates to apparatus for continuously shaping surfaces of one or multiple slabs of compressible or cellular polymer material, such as polyurethane foam. One or more blades cut portions of the cellular material from the slab or slabs after the slab or slabs have been compressed between compression rollers and a pair of movable patterned platforms.
Several methods and apparatus for cutting slabs of cellular polymer materials have been disclosed in the prior art. For example, U.S. Pat. No. 4,700,447 to Spann discloses convolute-cutting slabs of polyurethane foam by compressing a slab or pad of foam between a pair of rolls with opposed spaced projecting fingers arranged in a pattern and cutting the foam with a saw blade transversely just as it emerges from the rolls. The cut slab is then separated into two pads each with convolute-cut surfaces forming a series of peaks separated by valleys. The valleys on one pad are formed by slicing away foam which becomes a mating peak or projection on the other pad. Spann then shaves the peaks to form a more planar top surface. As noted in Spann, convolute cutting alone produces only rounded peaks and rounded valleys, and it is difficult, if not impossible, to produce a cut surface with peaks having substantially flat top surfaces or with recesses having substantially straight side walls. The convolute usually is intended to form the classic symmetrical and repeating xe2x80x9cegg cratexe2x80x9d pattern of peaks and valleys. To achieve a planar upper surface at other than the recessed portions the tops of the peaks must be cut or shaped in a second step.
Cellular polymer materials may also be cut using a hot wire cutter. A slab of such material is cut by moving the slab relative to one or more hot wires as shown, for example, in U.S. Pat. No. 4,683,791 (Demont). Only straight cuts in regular or symmetrical patterns may be formed using a hot wire cutter. See also U.S. Pat. No. 4,915,000 (MacFarlane) and U.S. Pat. No. 5,573,350 (Stegall).
Shapes may be cut into the surface of a slab of cellular polymer material using a punch cutting apparatus, such as disclosed in U.S. Pat. No. 5,299,483 (BerFong). A block of the cellular material is pressed against a template so that a portion of the material is forced through an opening in the template. The exposed material is then cut by a blade and removed, leaving a recess or cavity in the slab. This method cuts one block of material at a time, and only one surface at a time.
U.S. Pat. No. 4,351,211 (Azzolini) compresses a block of foam material against a template or die having an aperture therein using a pair of plates with concave and convex portions. The compressed foam is transversely cut along the template as it is held between the plates. More complex cut regions may be obtained than when using a template without the plates with raised and depressed portions, but only one block is cut at a time. Other template or pattern cutting methods are shown in U.S. Pat. No. 3,800,650 (Schroder) and U.S. Pat. No. 3,653,291 (Babcock).
The surface of a cellular polymer material may be shaped by molding or embossing, as opposed to cutting. U.S. Pat. No. 4,383,342 (Forster), for example, discloses injecting the foam-forming composition into a mold cavity. After sufficient curing time, the individual foamed article is removed from the mold. Other one-shot molding techniques and apparatus are known to persons of skill in the art. The molded cellular polymer product generally forms a tough skin at the surfaces that were in contact with the mold.
Continuous and semi-continuous molding processes are also known. These processes have the same drawbacks associated with one-shot molding techniques. For example, U.S. Pat. Nos. 4,128,369 and 4,290,248 (Kemerer, et al.) disclose an apparatus and method for impression molding thermoplastic products. The thermoplastic material in a liquid state is injected between compressed traveling belt molds. As the belt molds travel away from the point of introduction of the thermoplastic, they are cooled, which in turn cools the thermoplastic material, allowing it to solidify. The hardened molded thermoplastic material is removed from between the belts to form the finished product. Kemerer does not show a method for cutting or shaping a compressible and expandable cellular polymer material, such as polyurethane foam.
A method of embossing a foam surface using a patterned metallic embossing belt or band is shown in U.S. Pat. 4,740,258 (Breitscheidel). The foam is heated and then pressed against the embossing belt. The belt is removed after the foam surface cools. The embossed surface by design has a hardened skin. No method for cutting or shaping the foam is disclosed.
U.S. Pat. No. 5,534,208 (Barr) discloses a continuous rotary method for surface shaping synthetic foams in which the foam is compressed between a compression roller and a die roller having raised and recessed portions. The portions of the foam extruded into the recesses in the die roller are cut away. The compressed foam portions return to an uncompressed state after passing through the rollers. As a result, a mirror-image pattern to the pattern on the surface of the die roller is cut on the surface of the foam. The diameter of the die roller limits the length of the shaped synthetic foam article that may be formed. In addition, only one foam surface may be shaped with each pass between the die roller and the compression roller.
The prior art does not disclose an apparatus for continuously shaping a compressible or cellular polymer material of unlimited length by cutting to form recesses of various depths and various symmetrical and nonsymmetrical shapes. Nor does the prior art disclose a profile cut product without the hardened skin or hard spots associated with molded or embossed products. Nor does the prior art disclose cutting cellular polymer materials with an apparatus that includes a movable patterned platform, such as an endless belt or a series of connected panels defining at least one recess or void into which the cellular material may be compressed before cutting the material transversely with a knife blade.
An apparatus for continuously shaping a compressible or cellular polymer material, such as polyurethane foam, by cutting and removing portions of the material is disclosed. A pair of compression rollers which have interposed between them a pair of moving patterned platforms compress together the moving patterned platforms with one or more slabs of cellular polymer material held there-between. If one slab is used, portions of cellular polymer material from one face of the slab fill recesses or voids formed in the first moving patterned platform. Portions of cellular polymer material from the other face of the slab fill recesses or voids formed in the second moving patterned platform.
The apparatus may use a single knife blade and form two cut products from the single slab of cellular polymer material. The blade, positioned between the compression rollers and between the moving patterned platforms and closely adjacent the region in which the slab is compressed by the rollers, cuts the slab transversely just as it emerges from between the compression rollers. After leaving the apparatus, the cut slab is separated into two cut products that have on their cut surfaces pattern cut regions. The cut regions on the first product correspond in mating relation to the raised regions (projections) on the second cut product. Conversely, the cut regions on the second product correspond in mating relation to the raised regions on the second cut product.
The moving patterned platforms may be belts or panels or a series of panels that may be formed into a continuous path. Each of the moving patterned platforms may define several recesses that are separated or interconnected, symmetrical or nonsymmetrical, repeating or nonrepeating. The position of the recesses on one patterned platform need not correspond to the position of the recesses on the second patterned platform. Where the cellular polymer material is compressed so that it fills a recess in one moving patterned platform and there is no corresponding recess in the other moving platform, the knife blade will cut deeper into the slab creating a void in the part of the slab that is farther away from the recess and closest to the patterned platform without the recess. In other words, a greater amount of cellular material is forced to one side of the blade when it fills a recess in the patterned platform. Where the recesses in the patterned platform are complementary to one another, however, such that an equal amount of cellular polymer material is compressed within the recesses of identical depth in both platforms, in this region the slab will be split or cut transversely substantially nearly in the center of its thickness because a nearly equal amount of material is found on either side of the blade.
The apparatus using a single blade may also form two cut products from two slabs of cellular polymer material. In this embodiment of the invention, the two slabs in stacked relation are fed between the compression rollers and the movable patterned platforms. The blade is positioned as close as possible to the vertical midpoint between the outer patterned surfaces of the patterned platforms. Where the slabs are compressed between the platforms in regions where neither platform contains a recess, if the blade is centered between the platforms, no portion or no substantial portion of the surfaces of the slabs will be cut by the blade. Similarly, if both of the patterned platforms have recesses of equal depth, no portion or no substantial portion of either slab surface will be forced beyond the cutting edge of the blade.
If, however, a recess is formed in the region compressed between the compression rollers of one platform and there is no corresponding recess formed in the corresponding region of the other platform, then a portion of the cellular material from one of the slabs will be forced beyond the blade edge and the cellular material will be cut such that a recess will be formed in the surface of the slab. The slab adjacent to the platform without the recess will be forced beyond the blade edge and cut by the blade. Alternatively, if a recess of one depth is formed in the region compressed between the compression rollers of one platform and a corresponding recess of a different depth is formed in the corresponding region of the other platform, cellular polymer material will be cut from the portion of the slab that is forced beyond the blade. The slab adjacent to the recess of greater depth likely will be compressed away from the blade so that the slab adjacent to the recess of lesser depth will be compressed with a portion forced beyond the blade for cutting. The depth of any recesses formed in the surfaces of the slabs will depend upon the compression factor of the cellular material and on the depth and placement of the recesses in the patterned platforms.
Where two slabs in stacked relation are fed through the compression rollers and between the patterned platforms, each slab is cut to form profile cut surfaces with recesses. Waste material cut from the slabs is removed. Unlike the result when only one slab of foam is cut by the apparatus, the surfaces of the two cut slabs do not nest together.
If it is desired to obtain two cut products with mirror image cut patterns on their surfaces simultaneously, the apparatus may be used with two blades. With this embodiment of the invention, two slabs in stacked relation are fed between the compression rollers and the patterned platforms. The two blades are positioned nearly adjacent to the vertical midpoint between the surfaces of the patterned platforms and near the point at which the slabs emerge from between the rollers. The slab surfaces in contact with each other when the stack is fed between the rollers are the surfaces subject to being cut by the blades. Each blade cuts a portion of the slab surface where the slab material is forced beyond the blade, forming cut portions that correspond in pattern and shape to the pattern and shape of recesses formed in the opposite patterned platform. The depth of cut will vary by the compression factor of the cellular polymer material.
Alternatively, the upper and lower surfaces of a single cellular polymer material slab fed between the compression rollers may be profile cut simultaneously using the apparatus of yet another embodiment of the invention. First and second blades are provided just at the point the compressed cellular material emerges from the compression rollers. The second blade is spaced apart from the first blade, such that the first blade cuts portions of the upper surface of the slab and the second blade cuts portions of the lower surface of the slab. The cut portions are removed, leaving the finished profile cut product that emerges from between the two blades. With this embodiment of the invention, complex cut profiles may be formed in the upper and lower surface of the slab. The cut portions may be interconnecting or complementary to one another. Portions of the slab in one surface region may be cut simultaneously as portions of the slab in the opposite surface region are cut. Fine patterned shapes not heretofore achieved by continuous cutting methods for cellular materials may be formed using this apparatus.